1. Field of the Invention
The invention relates to a composite bar, in particular for window or door frames (both outer frames and sashes) and rolling shutters. Such a bar or rod can also be used for other purposes, for example for forming a folding shutter frame or walls made up of such bars for barracks, dismantlable houses and the like.
The plastic hollow profile bar is preferably made of thermoplastic plastic. It may comprise solid plastic as well as foamed plastic, in particular integral foam, preferably in each case of PVC.
2. Description of the Prior Art
A known window frame of composite bars surrounds a window pane, for instance of insulating glass or a door leaf which possibly may also have a particular heat-insulating effect.
Furthermore, rolling shutters are known comprising plastic bars in the cavities of which stiffening metal profiles are inserted which extend over the width of the cavities.
Now, door frames, window frames and sashes, rolling shutters and the like are required to have a good heat-insulating effect. It is also necessary for these frames and shutters to be particularly stiff with respect to forces applied perpendicularly to the plane of the window pane or door leaf or shutter.
A plastic window frame is already known (DE-PS No. 1,281,664) in which near the outer surface (weather side) and inner surface (indoor side) in each case a flat steel member parallel to the surface is inserted. Perpendicularly to the flat steel members, i.e. in the direction of any heat gradient occurring, two flat steel members are also inserted.
Whereas the flat steel members lying in each case parallel to the outer and inner surface hardly make an appreciable contribution to the aforementioned stiffness, the flat steel members disposed perpendicularly thereto extend in the direction of the heat transfer and thus form quite considerable heat bridges and consequently very much impair the insulating effect of the frame.
Instead of four flat steel members, it is also known to insert a closed rectangular metal profile having two flanges which lie respectively parallel to the inner and outer surfaces and two webs which connect the flanges together. Due to the connection of the flanges and webs, a closed hollow beam results which is exceedingly resistant to bending and thus imparts the desired stiffness to the profile section. However, in this case, as well, there is the disadvantage that the metal webs joining the two flanges form a heat bridge. The same disadvantage is present in the known rolling shutter bars with inserted metal stiffening bars.